The present invention relates to a railway system and more particularly to a method for saving energy by controlling power output by railway substations and controlling drive force of groups of trains.
Recently there has been an increase in the number of passengers using train lines in commutable areas of large cities and in principal trunk lines connecting such cities. In the Yamanote of Japan for instance, a super-overcrowded train exceeding traffic congestion rate of 150% has become common during the rush hours in the morning. Under these circumstances, respective railway companies are planning to relieve traffic congestion by operating of extra trains, making up of longer-coach (carriage) trains, introduction of no-seat trains and so forth. However, it has already become impossible to operate extra trains during the morning and evening rush hours.
The limits of the capacity of railway substations may be mentioned as one of the reasons for the above. An example of a feeding method by railway substations will be described with reference to FIG. 1. Reference numerals 1 to 11 in FIG. 1 represent trains, 12 represents a trolley cable or pantograph feed cable, 13 represents a track rail, 101, 102 and 103 represent railway substations, and 104, 105 and 106 represent electric power supply territories of the railway substations 101, 102 and 103, respectively. Besides, the electric power supply territories 104 to 106 vary to some extent depending on difference of voltage between a railway substation and an adjacent railway substation, and do not correspond to ordinary territories among stations.
In an electric railway (hereinafter referred to as a railway), trains are operated by such a method that railway substations (hereinafter referred to as substations) 101, 102 and 103 convert electric power supplied by a power plant to predetermined specification. The electric power is supplied to trains 1 to 3, 4 to 8 and 9 to 11 located in electric power supply territories 104, 105 and 106, respectively, through the trolley cable 12. One substation usually supplies electric power to four to five trains which may be present on the railroad lines in the suburbs of big cities. A train consumes electric power at a time of accelerating control. A train is frequently required to perform acceleration and deceleration control in departing from a and entering station since the distance between adjacent stations is generally short for commuter trains in urban districts of large cities. Even if a departure timing between trains has been adjusted in a railway schedule, variations of these departure times practically for every train due to delays resulting from various primary factors. Thus, it is difficult to stagger the departure timing perfectly. When an operation interval is shortened hereafter so as to increase the frequency of trains source under the above circumstances, power consumption is increased temporarily. Also a notable peak is generated in the substation output since the probability that a plurality of trains perform power running at the same time in the same electric power supply territory is increased. In the prior art, however, a substation does not provide control for restraining the output peak power. Further, timing of power running and a decision of notch steps in a train group are based on their reference rules determined only for each individual train. Further a power output state of a substation and states of other trains located in the same electric power supply territory are not taken into consideration.
According to the above-mentioned prior art, since a power consumption peak is increased, it becomes difficult to cope with such a state with the present substation capacity. Further, system designed with a capacity of at least the temporary peak of power consumption produces useless overcapacity of in the installations. Furthermore, since electric rates contracted by a substation are decided with constant consumption as a reference, expensive additional rates are charged for a temporary peak exceeding the extent of the contract, which causes increased transportation costs.